This invention relates to automobile engines in general and in particular to intake and exhaust valves that can be kept open for a variable amount of time, and the point in the combustion cycle at which the valve opens can be varied.
It is known that the optimum length of time the intake valve is kept open on the intake cycle will vary with conditions. For example, as an engine runs faster, the intake valve should be left open longer to allow the same volume of air and fuel into the cylinder. Also, if the engine is run at higher elevations where atmospheric pressure is less, the intake valve should be left open longer to get the same volume of air into the cylinder.
Previous attempts to solve this problem have not met with great success. One prior art method to solve this problem increased the length of the stroke of the intake poppet valve at high speeds. This was accomplished by using a second cam with a larger lobe, that would engage when the revolutions per minute (rpm) exceeded a certain value, pushing the poppet valve further into the cylinder, thus keeping the valve open longer.
This worked well in some instances but had some significant drawbacks. The binary positioning of the valve was not conducive to optimum engine output over the entire range of engine speeds. That is, the valve had only two open positions, and was shifted from one to the other at a fixed, nonvariable rpm value.
Other prior art attempts to achieve the objectives of this invention have not succeeded. Mingers FR2608-67-A discloses an electronic control system and alters the position of the cam shaft relative to the crankshaft depending on engine operating conditions. This, however, does not vary the length of time the valve is open or shut during the engine cycle, does not provide for maintaining the motor deenergized. During the open or shut position as in the present invention, Huber DE3307-852-A shows a cam follower which is slidable to change the curvature of the cam follower presented to the cam. This changes the point in the combustion cycle that the valve opens and closes. It does not, however, change the length of the time the valve is open as in the present invention.